It is quite often desirable to test or sample a bore hole or well for determining the characteristics of a zone, such as pressure, or for determining the content of a fluid or, vapor or gas flowing therein. Hereinafter, fluids, vapors and gases are collectively referred to as fluids. More recently, the sampling of ground water has become vital in view of toxic and other contaminant pollution. Because the earth is made of various different formations or layers of materials, ground water and other fluids within the earth, in general, travel in these specific layers. It is often quite difficult if not impossible, without physical excavation, to determine the size and location of specific layers, let alone determining the contents of the fluid flowing therethrough. However, it is important to locate such layers or formations so that, for example, a layer or formation that has been contaminated by toxic waste may be located and action taken for the prevention of harm to life. Other reasons for locating specific layers include locating a formation or layer containing or leading to minerals or other valuable commodities, such as petroleum.
Various devices have been conceived and utilized in the past for isolating a zone within a bore hole or well and testing or sampling the fluid of the isolated zone. These devices, in general, include a lower and an upper packer that through, for example, air pressure, create a seal with the well casing or bore hole surface and fluid from the isolated test zone is drawn as needed. However, the packers of these devices are fixed at a given distance from one another and, therefore, although the zone location within the bore hole or well may be varied, the longitudinal length of the test zone cannot. This presents a serious drawback because earth formations vary in thickness and, as a consequence, an accurate sampling of a specific layer is quite often difficult to obtain without varying the longitudinal length of the test zone.
Prior art devices are also undesirable in that they quite often require a pressurized air supply for operation. Further, a positive seals between the well casing and the packers are quite often not provided and, as a consequence, the sampling is inaccurate in that it includes fluid from outside the test zone that has leaked through the seals. Aside from the inconvenience of having to utilize a pressurized air supply, because the strength of the well casing varies along the longitudinal length thereof and the air pressure to the packers is not often accurately controlled, the well or screen casing is quite often broken rendering the well or screen substantially useless.
Accordingly, a need exists for an apparatus for isolating a testing zone in a bore hole casing wherein the longitudinal length of the test zone as well as the location of the test zone in the casing is selectively variable. The plugs or packers used for creating the test zone should be easy to operate without the need for pressurized air and should provide a positive seal between the plug or packer and the casing. Further, the apparatus must generally be inexpensive to manufacture yet generally easy to operate, reliable, and long lasting.